1. Field of the Invention
This invention relates to pyrrolo[3,2-e]pyrazolo[1,5-a]pyrimidine derivatives and their salts possessing excellent vasodilative, antihypertensive, antihyperlipemia, platelet aggregation suppressing, Ca.sup.++ blocking, and bronchodilative activities, and to a medicine comprising a pyrrolo[3,2-e]pyrazolo[1,5-a]pyrimidine derivative or its salt as an effective component.
2. Description of the Background Art
In today's society in which life-spans are prolonged circulatory diseases have become a major cause of death along with malignant tumors.
One effective way of treating circulatory diseases is to lower the blood pressure by a vasodilator and to promote the blood circulation. Suppressing platelet aggregation is a useful way of inhibiting the formation of arterial thrombosis. Many compounds possessing Ca.sup.++ blocking activity also have an antiarrhythmic activity. Moreover, many of the diseases relating to circulation are closely associated with each other.
Accordingly, development of a medicine which is effective for all of these circulatory diseases has been desired.
On the other hand, bronchial asthma is a disease involving abnormal contraction of bronchial smooth muscle, swelling of bronchial mucosa, secretion of mucus, and the like, all of which are considered to be caused by various exogenous and endogenous factors, even though the mechanisms involved remain to be elucidated. For this reason, a symptomatic therapy using medicines rather than a therapy eliminating the cause of the disease are mostly used.
Major medicines currently used for curing bronchial asthma are .beta.-receptor stimulants. The only other medicine used for this purpose is theophylline. These medicines, however, have many side effects, and, because of this, their doses and the period of administration have to be limited.
Development of medicines for curing bronchial asthma, e.g. a bronchodilator, with minimal side effect has therefore been sought.
In view of this situation, the present inventors have undertaken extensive studies and found that compounds represented by the following formula (I) had excellent circulatory disease curing activities as well as bronchodilation activities. This finding has led to the completion of the present invention.